Envelope stuffing machines, for example of the type shown in U.S. Pat. No. 2,736,999 issued Mar. 6, 1956 to F. J. Rouan, et al., U.S. Pat. No. 2,914,895 issued Dec. 1, 1959 to S. W. Martin, U.S. Pat. No. 4,077,181 issued Mar. 7, 1978 to L. K. Asher, et al., and U.S. Pat. No. 4,169,341 issued Oct. 2, 1979 to F. T. Roetter, et al., all of which patents are assigned to the assignee of the present invention, generally include: structure for 15 delivering an envelope, with its address panel oriented upwardly and its flap opened, to a registration gate at an enclosure inserting station; structure for timely opening the delivered envelope, including a plurality of fingers known in the art as stripper fingers, which are insertable into the throat of the envelope for opening the same; and structure for inserting an enclosure into the opened envelope. More particularly, the envelope opening structure of these devices includes a plate which acts as a ledge upon which the flap of the envelope is located when it is delivered to the inserting station. And, although none of the aforesaid patents show the same, the assignee of the present invention has for many years provided in its Model 3320 Table Top Inserter, one or more rigid finger members, known in the art as depressor fingers, which are fixedly attached to the framework of the Inserter and disposed in overhanging relationship with respect to the envelope's address panel, for depressing the body of the envelope's address panel downwardly against the resistance afforded by the envelope flap ledge, for partially opening the throat of the envelope to facilitate insertion of the stripper fingers into the envelope.
In U.S. Pat. No. 4,337,609 issued Jul. 6, 1982 to D. H. Foster, et al. and assigned to the assignee of the present invention, there is shown an envelope stuffing apparatus which includes a enclosure ram, a pair of outfeed push rollers and stripper fingers. The ram comprises a reciprocal ram plate having a depending portion which engages the enclosures. On the forward stroke of the ram plate, the plate carries therewith the enclosures into the throat of the opened envelope. As is well known in the art, the ram plate also moves the stuffed envelope downstream into feeding engagement with the outfeed rollers. Accordingly, the ram and outfeed rollers cooperate with each other for removing stuffed envelopes from the insert station.
The ram envelope stuffing apparatus of the above type has been successfully employed for many years. Although working well, there is a limitation on the throughput at the insertion station because of the reciprocating action of the ram plate. Typically, the ram insertion station operates well at a rate less than 6000 cycles (or envelopes per hour) for #10 (4 inch by 9 inch) envelopes. The rate of operation varies for different sized envelopes.
Improvements have been made recently in the throughput of the upstream modules of the inserter machine. An example of recent improvements is in the area of a dual accumulator described in U.S. Pat. No. 519,199 filed May 4, 1990, also assigned to the assignee of the present invention. However, the insert station employing the ram plate cannot take advantage of the improvements to the throughput of the upstream modules. This is, in part, due to the physical constraints associated with the ram mechanism, and, in part, to the motion inherent in the operating ram. Attempts at increasing the throughput of the ram type insert station has resulted in severe vibrations as the mass of the ram reciprocates at higher speeds. Such vibrations induce severe life shortage of the parts in the insert station. In addition, the reliability of the insert station decreases significantly at the higher speeds.